The separation of a gaseous mixture into constituents is useful for a number of industrial and commercial applications. A particular methodology relies on an aerodynamic separation nozzle to urge various gas species comprising a mixture to be separated as a result of pressure and temperature decreases experienced during supersonic expansion. Adiabatic cooling of the gas mixture during the expansion results in the phase change of one or more of the constituents into a non-gaseous phase, typically liquid, and subsequent separation based on differing phases is enabled. See e.g. U.S. Pat. No. 3,528,217 issued to Garrett, issued Sep. 15, 1970; U.S. Pat. No. 6,280,502 issued to van Veen et al., issued Aug. 28, 2001; U.S. Pat. No. 6,372,019 issued to Alferov et al., issued Apr. 16, 2002; U.S. Pat. No. 6,513,345 issued to Betting et al., issued Feb. 4, 2003; and U.S. Pat. No. 7,318,849 issued to Betting at al., issued Feb. 4, 2008, among others. These devices generally specify a supersonic expansion, phase change of a constituent, and subsequent separation based on the differing phases.
Various separation methodologies are employed following the supersonic expansion. For example, when phase change to liquid is employed, the flow path of the gaseous stream at a supersonic or subsonic velocity may be altered so that the gaseous component avoids a perforated wall while centrifugal forces force the impingement of the liquid phase against the perforated wall, affecting a degree of separation. See e.g. U.S. Pat. No. 3,528,217 to Garrett. Another common approach has been to effect separation following a supersonic expansion by imparting a swirl to the supersonic gaseous stream, and allowing the resulting centrifugal forces to affect a stratification where the liquid or solid constituent resides substantially in a layer adjacent to the walls of a test section while the gaseous phase resides substantially toward the center of the flow. Following the stratification, various means including annular flow passages, perforated walls, and combinations thereof are utilized for final separation. See e.g. U.S. Pat. No. 6,280,502 to van Veen et al., U.S. Pat. No. 6,372,019 to Alferov et al., and U.S. Pat. Nos. 6,513,345 and 7,318,849 to Betting at al.
The centrifugal stratification relied upon by the above devices requires that thermodynamic conditions at the wall, where the liquid or solid constituents collect, be maintained such that the solid or liquid constituent remains in the non-gaseous phase. Depending on the gaseous constituent to be separated, this can levy significant additional requirements aimed at prevention of heat transfer from the surroundings to the wall portion of the supersonic device, in order to establish conditions where the liquid or solid constituent is maintained until separation occurs. The supersonic expanding flow also generates viscous boundary layers at the wall, which further complicates a process whereby swirling flow is intended to generate and maintain a liquid or solid constituent residing at the wall. Additionally, generating swirl in order to create the rotating supersonic flow levies additional complexities geometric or otherwise within the supersonic nozzle itself.
It would be advantageous to provide an apparatus and method for the removal of a gaseous constituent from a gaseous stream utilizing a supersonic expansion where the thermodynamic conditions and boundary layers at the wall were less relevant. It would be further advantageous if the removal could occur without the additional complexities generated by the necessity of a supersonic swirling flow.
The aforementioned references further are designed to create separation in the gaseous mixture at a supersonic velocity, and are not particularly compatible with existing separation devices designed for subsonic flows. An apparatus and method where a supersonic expansion and deceleration is utilized to facilitate phase change, and which subsequently decelerates the flow to a subsonic flow while maintaining the phase difference, would allow use of existing separation devices with a minimum of modification. Such an apparatus and method could utilize, for example, existing centrifugal separators designed for subsonic centrifugal separations.
One device frequently utilized for the deceleration of supersonic flows is the supersonic diffuser. Diffusers generally convert the kinetic energy of a supersonic fluid at the diffuser inlet into an increased pressure at the diffuser exit. A common application is following a supersonic wind tunnel test section, where an exit diffuser may be present in order to reduce the pressure ratio required for wind tunnel operation. Typically in the diffuser, a converging geometry creates a series of reflecting oblique shocks which gradually slow the supersonic flow until a weak normal shock brings the flow to subsonic speed. A divergent section may continue to slow the flow and increase pressure. Another common application occurs in the provision of combustion air to aircraft designed for operation at supersonic velocities, where a variable diffuser typically creates oblique shock waves in order to facilitate air flow to the combustion process. These applications utilize the known propensity of an oblique shock to reduce the pressure loss associated with deceleration to a subsonic velocity as compared to a normal shock at a given Mach number. However, these applications and others are typically concerned with maximizing pressure recovery given other constraints, and the specific temperature and pressure profile that a decelerating gas traverses en route to subsonic velocity is generally secondary. For gaseous separation methodologies, it would be advantageous to utilize a diffuser whereby the supersonic flow could be decelerated to subsonic flow following a temperature and pressure profile which maintains the constituent to be separated in a non-gaseous phase.
Accordingly, it is an object of this disclosure to provide an apparatus and method whereby a supersonic expansion and deceleration is utilized to facilitate phase change of a gas constituent, and where subsequent deceleration to subsonic flow occurs while maintaining the phase difference, such that a final separation could occur at a subsonic velocity.
Further, it is an object of this disclosure to provide an apparatus and method whereby the phase change of a gaseous constituent resulting from a supersonic expansion and deceleration is maintained during a subsequent deceleration to subsonic velocity, allowing for utilization of existing separation devices with a minimum of modification
Further, it is an object of this disclosure to provide an apparatus and method whereby a supersonic expansion and deceleration is utilized to facilitate phase change of a gas constituent and where the phase change can be maintained with a mitigation of viscous boundary layer impacts.
Further, it is an object of this disclosure to provide an apparatus and method whereby a supersonic expansion and deceleration is utilized to facilitate phase change of a gas constituent and where separation of the gas constituent and a carrier gas can occur in the absence of additional complexities generated by the necessity of a supersonic swirling flow.
Further, it is an object of this disclosure to provide an apparatus and method whereby an oblique shock diffuser decelerates a supersonic flow comprised of a carrier gas and a gas constituent by facilitating a temperature and pressure profile such that the constituent is present in a non-gaseous phase at a subsonic velocity.
These and other objects, aspects, and advantages of the present disclosure will become better understood with reference to the accompanying description and claims.